Thyroid cancer refers to any of five kinds of malignant tumors of the thyroid gland: papillary, follicular, hürthle cell, medullary and anaplastic. Papillary and follicular, and hürthle cell tumors are the most common: they grow slowly, may recur, but are generally not fatal in patients under 45 years of age. Medullary tumors have a good prognosis if restricted to the thyroid gland and a poorer prognosis if metastasis occurs. Anaplastic tumors are fast-growing and respond poorly to all therapies.
Thyroid nodules are diagnosed by ultrasound guided fine needle aspiration (USG/FNA) or frequently by thyroidectomy (surgical removal and subsequent histological examination). As thyroid cancer can take up iodine, radioactive iodine is commonly used to follow and treat thyroid carcinomas, followed by TSH suppression by thyroxine therapy.
Thyroid cancer is the most common endocrine malignancy, with 33,500 new cases of thyroid cancers estimated to be diagnosed in the U.S. in 2008. Differentiated thyroid carcinoma comprises 90% of all cases. Once thyroid cancer metastasizes to distant sites and is no longer amenable to radioactive iodine therapy or surgery, expected survival declines rapidly. The only FDA-approved therapy for these patients is doxorubicin.
To date, no effective therapy is available for treating metastatic cancer that is not amenable to radioactive iodine therapy or surgery. Accordingly, a need exists for improved methods and compositions for treating thyroid cancer.